In order to be a proper prefix, the actor url must end with a '/'
otherwise it can match another user that starts with the same prefix:
for example 'testuser' will match anything made by 'testuser2'
users' follower/following/post counts and their posts when viewing profiles in Mastodon-compatible apps (Fedilab, Tusky, etc.).
Fixes for Moshidon and improvements for better compatibility with HAProxy